Process for the preparation of ethyleneurea



Patented Aug. 12, 194'? PROCESS FOR THE PREPARATION OF ETHYLENEUREA Donald J. Loder, Wilmington, Del., assignor to E. I. du Pont de Nemours 8; Company, Wilmington, Del., a corporation of Delaware No Drawing. Application March 1, 1944, Serial No. 524,520

10 Claims. 1

This invention relates to a process for the preparation of N.Nethyleneurea, and more particularly to its preparation from ethylene glycol and urea. This case is related to the following applications: S. N. 524,522 of A. T. Larson and D. J. Loder; S. N. 524,523 of H. R. Dittmar and D. J. Loder; and S. N. 524,524 of A. T. Larson, D. J. Loder, and H. R. Dittmar, all filed on even date with the instant application.

N.Nethyleneurea, hereinafter referred to as ethyleneurea, and otherwise known as 2 x0 imidazolidin and imidazo1idon-(2), has been made by heating ethylene diamine with diethyl carbonate at 180 C. [E. Fisher, Koch, A 232, 227 (1886)], by warming an aqueous solution of N.N'ethy1ene thiourea with freshly precipitated mercuric oxide [Klut Ar. 240, 677 (1887)], and by distillation of aqueous N.Nethylene guanidine under diminished pressure [Pierron A 9, (11) 363 (1908)].

An object of the present invention is to provide a process for the preparation of ethyleneurea. Another object of the invention is to provide a process for the preparation of ethyleneurea from ethylene glycol and urea. A further object is to provide improved procedural details for the preparation of ethyleneurea, including eflicient and economical methods for transformation of the product obtained from the reaction of ethylene glycol with urea to ethyleneurea. Other objects and advantages of the invention will hereinafter appear.

The above objects are realized by a process wherein ethyleneurea is prepared from urea and ethylene glycol by an economical process giving commercially acceptable yields of the product. The process involves three main steps:

1. Reaction of urea with ethylene glycol to form a crude reaction mixture or melt containing ethyleneurea and potential ethyleneurea.

2. Transformation of the crude reaction mixture or melt to convert the ethyleneurea potentially present to ethyleneurea by treatment with water.

3. Purification of the ethyleneurea and separating it from the water-treated crude product.

The first step of the process is conducted by dissolving urea in glycol, gradually heating the solution to reaction temperature and holding it at temperature until the reaction has proceeded to the desired extent. The reaction is conducted in a suitable converter, preferably provided with a reflux condenser and an ofi-gas scrubber. During the initial stages of the reaction, some glycol vapor is condensed in the reflux condenser and is returned to the reaction zone, while the remaining vapors, ammonia and carbon dioxide, pass through the reflux condenser to suitable scrubbers'for their recovery. At the end of the reaction period, the product, a viscous'liquid (which may be a solid when cooled) containing ethyleneurea and potential ethyleneurea, is discharged into water or other suitable solvent.

This step of the reaction is conducted at temperatures ranging up to 200 or 250 C. pr above.

At temperatures above 250 C., however, the crude product is somewhat darkened in color, and accordingly it is found preferable to carry out the reaction at temperatures ranging between 100 and 250 C., the temperature being increased gradually to maximum temperature, the time required to heat the reactants from in the proximity of C. to about C. being in the neighborhood of from 2 to 8 hours, and from 175 to about 250 C. in the neighborhood of from 2 to 6 hours. the total time of reaction ranging from 4 to 24 hours.

It has been found that the reaction mixture of ethylene glycol and urea should be heated to a temperature of at least 200 C., and preferably 225 C. prior to the termination of the reaction, irrespective of the ratio of reactants. For example, if a reaction mixture containing an excess of ethylene glycol, say, 'in the order of2 moles of ethylene glycol per mole of urea, 'is

' heated under atmospheric pressures to its boiling point and maintained at that temperature for an appreciable period of time, substantially no ethyleneurea is produced nor can there be '7 obtained from such a reaction mixture any ethyleneurea by the water-treat g processmore fully particularized hereinafter. In order to obtain ethyleneurea in optimum amounts, high temperature treatment is required, and if glycol is present in excess, it is necessary to conduct the reaction under pressure which may be induced or autogenous in order that the reaction may be conducted at the higher temperatures; pressures ranging above 5 atmospheres to 100 atmospheres or higher may be used. In the event that the reaction mixture contains an excess of urea, such a mixture, even under atmospheric pressures, can generally be heated to 'a temperature in the neighborhood of 225 C.. and consequently pressure treatment in this instance is not required to reach temperature, but'may be employed if desired. l I

The grade of the glycol employed is not critical, although pure ethylene glycol will give most. satisfactory results. The urea employed should for best results likewise be pure' a1thoughfir1or -,1 mally occurring impurities found in synthetic" urea do'not appear to deleteriously affect the re: i action. Inasmuch as the reaction temperature is well above the boiling point of water'the use i of anhydrous ethylene glycol and crystal. urea eliminates the necessity of boiling'off' the water:v introduced by aqueous solutions of these mate rials and also avoids loss of urea by hydrolysis.

It has been found that the ratio of urea to ylene g co o a. w i h a sh uld. range pref rablybetweenrom .3 9 moles o the; u ea pe molepf; theeth lenes r ol with the pref rred ra e etween 3 an -6. m l ea r ole i he ly ol- T e sol tion of ur a in. ethyl: n ycol. shou d preferably. c t in at least 'wfljur a nd at ea t. th l n ycol by ei ht The. above p op r ion arep eferred, alou was. st te ethyleneurea can be ob; ained W th'ianexcess of e ene. glycol prese. n ..i.f't. .e.des e eteo eact on c nditi ns are used. 40

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The invention covered by theha llfif firtimltis; ri re lti directe t reatm n fe p oduct ob ain d. esc ib d. nder stee with. W

attl r. ere prer thyleheu ee.unionism: y. zese t Thewa er tre tment results n he reesi rmat ou of pote t y. av i ab e.

E h len nrea is traeisstematoa -Qi-t e. productrrom stepnne smsse hrou h hee d u or mtqa 13 1 5."; 7

on ucted ml sure-resisting autoclave. The crude product, usually a melt, from synthesis charges containing 5 moles of urea per moleof glycol is preferably diluted with, in parts by weight, 2 parts of water per 3 parts of melt prior to treatment. As dilution with water below about 30% causes separation of a heavy, semi-solid phase which tends to clog pumps, the concentration of melt is preferably kept above this amount. Optimum concentrations for melts prepared from 4 to 6 moles of urea per mole of glycol is between 30 and on a weight basis, The dilution is preferably accomplished by dumping the hot melt directly into the cold water with agitation, the melt during its rapigiz co olin g beinggcqmminuted and thereby rapidly: dissolved and/or! dispersed into the water.

The temperature of the water treatment should bebetuleen 200. and 300 C. and preferably between 250 and 280 C., although higher, and for that matter lower, temperatures may be employed according. to thetime 'of contact. For example,

' at 250 (3., time oicointact in the order of '70 min- 'utes for optimum transformation may be cut to 2 5 minutes with temperatures in the order of 37939, Pressures are not critical, except in so far as it is necessary to maintain the mixture in the liquid phase to obtain most eflicient use of the pressure equipment. 1 They may range from 1-0.;to. 1.0.0. atmospheres or -higher.

- Alternatively the product'ot step mal or-superatmospheric pressures, wherein the ethyleneurea present is distilled over while the potential ethyleneurea is converted during the steam distillationto'.ethyleneurea and also distilledover. In addition to. effecting such" a tran'stormation,

steam distillation likewiseiaidsin separatingjthe V fication by rectif cation of theethyleneurea-trom the .DLQQU-Gt obtained from thelprocess of thesesondgstep. v A.s.uit2 ;.ble still, forexample,is charged with the productofi thesecond. step,-watenand dissolved gases stripped off at atmospheric-pros sure the pressure .is reduced andiintermediate byproducts and the ethyleneurea. distilled T e. retinedgethyleneurea may. be. discharged- 1 from the purifying stillvreceiverdirectly-toiaro- .kenroll uponwhich the ethylene s the rollzrevolves. Theprdd-uct to. give material; Sinceethylen'eurea tends. to form ;a .hemiehys 'gate, humid. air is. excludeghfrom. the. operation. and: theipackagingofs theproduct. .5 59:" Alter natiwely, the. product .from; .stepl'twoi may bJ .l slrto. crystallization.for tlieeseparation leneureathe.crystalligationbeingiconducted; agsl tablecsolyent therefor. 1:.

Examples ;ar e ,.nowegiven. illustratingxpre erred ;the myentiomwhereimparts are essiotherwiseindicated} ave,- przoyidediwith areflux condenser and Qh l fgedai with 12 02;. parts. orurea dissolved in:

3.55 parts of glycol, molecular weight ratiooi '1' may be subjected to. steam distillation under. sub-, nor-- efarom. a suitableldoctoreknitet e. first: step. of the-process owes -asi'lvereiinedtpressureeresisting aes 5,627

The crude melt Obtained by the above first step of the process was discharged directly and without cooling into 1 pounds of water per pound of melt. The resulting mixture was further diluted to give a mixture containing 6.3 parts of melt to 9.5 parts of water, and the resulting mixture was continuously introduced at the rate of 18 cc. per minute into a tubular, pressure-resisting converter consisting of a helical coil of ap proximately inside diameter and in length. The melt was heated in this coil to a temperature of approximately 250 C. under a pressure of approximately 500 lbs. per sq. in.; the contact time of the mixture at temperature was approximately 35 min. 1

The thus treated product from the second step was charged into a, suitable still, and the dissolved gases and water stripped from the mixture under atmospheric pressure, using a 1:1 reflux ratio and a pot temperature rising to a final value approximately between 150 and 170 C. By-products Were then removed by distillation under pressure of approximately 70 mm. mercury absolute pressure, and a pot temperature up to 190 to 200 C. The resulting residue was fed into an evaporator and cyclone separator in which it was separated into semi-refined ethyleneurea as distillate and high boiling by-products as residue, under 5 mercury absolute pressure, at a temperature of about 250 C. The semi-refined product was then further purified by distillation in a batch-still, under a head pressure at 5 mm, mercury absolute. The ethyleneurea distilling at a head temperature of approximately 179 C. The ethylene urea was obtained in a conversion based on the glycol of 55%.

Example 2.-A. 360 parts of urea were dissolved in 93 parts of ethylene glycol giving a molar ratio of 4:1 urea to glycol, and the resulting mixture is gradually heated in a suitable reaction vessel to a temperature between 160 to 180 C. over a period of 6.5 hours, from a temperature of 180 to 240 C. over a period of 3 hours, and at a temperature of 240 C. for one hour. 172 parts of crude melt was recovered and subjected without Water treatment to simple vacuum distillation for the recovery of ethyleneurea. Th conversion of ethylene glycol to ethyleneurea was approximately 25%.

B. A reaction converter was charged with 1680 parts of urea and 434 parts of ethylene glycol, giving a mole ratio of 4: 1. The reaction was carried out under substantially identical conditions as those employed in A, and 830 parts of the crude melt was produced. This crude melt Was sub- J'ected to transformation in accord with the second step of the process, conducted substantially in accord with that step as described in Example 1. From this transformed crude melt ethyleneurea was recovered with a conversion of approximately 55% based on ethylene glycol.

The table represents a series of examples conducted substantially in accord with the procedure described in Example 1 for the first step, except for the variations in concentrations, temperatures and other items noted, with the procedure of Example 1, except as stated under column 8, for the third step. The continuous procedure of step 2 is illustrated by step 2 of Example 1, while the discontinuous procedure may be carried out batchwise in a suitable autoclave under the conditions specified in the table.

Table Example numbers STEP I Charge (parts by weight):

Pot temp.start, 0-- 140 140 150 144 Pot temp.end, C 253 253 253 251 251 225 Time to 0., hrs... 8.5 8. 5 8. 5 8.0 8.0 6.0 Time 175 to Max. Temp 5. 5 5. 5 5. 5 4.0 4.0 5. 0 Time at Max. Temp 4. 5 4. 5 4. 5 0 0 0 Weight of crude melt 33 33 33 5. 99 5. 99 20. 4

STEP II Discontinuous:

Wt. ratio, melt:water Pot temp, Pressure, p. sq. in..- Total time, hrs Continuous:

Crude melt, lbs Water, lbs Solids, per cent Temp., C Pressure, p. sq. in s. Contact time, hrs

STEP III (Same as Example 1) Conversion glycol to ethyleneurea 47. 8 51. 5 42. 2 54 55 l 22 1 Crystallized.

All steps of the process may, if desired, be carried out continuously, the first step by passing the mixture of ethylene glycol and urea through a heated tube of relatively great length to diameter, the how being so controlled that the above described temperature cycle is used; the second step, by utilizing the continuous process, as described above; and the third step by passing the products of the first and/or second step through a suitable rectification process.

I claim:

1. In a process for the preparation of ethyleneurea from ethylene glycol and urea, the steps which comprise discharging the reaction product, obtained by heating ethylene glycol and urea, the urea being present in excess, into water, heating the resulting mixture to a temperature between 200 and 300 C., and subsequently recovering the ethyleneurea from the thus heated mixture.

2. In a process for the preparation of ethyleneurea from ethylene glycol and urea, the steps which comprise discharging the melt obtained by heating ethylene glycol and urea, the urea being present in excess, to a temperature between 150 and 250 0., without cooling, into Water, heating the resulting mixture to a temperature between 250 and 280 C. and subsequently recovering ethyleneurea therefrom.

3. In a process for the preparation of ethyleneurea from ethylene glycol and urea, the steps which comprise discharging the product from a reaction between from 4 to 6 moles of urea per mole of ethylene glycol on a weight basis conducted at a temperature between 100 and 250 C., without cooling, into water to give a mixture containing from 30 to 70% of the crude reaction product, heating the resulting mixture to a temperature between 200 and 300 C. and final1y's'epa-' rating ethyleneurea therefrom.

4. In a process for the preparation of ethyleneurea from ethylene glycol and urea, the steps which comprise discharging, into water, and without cooling, .the product from a reaction between moles of urea and 1 mole of ethylene glycol conducted at a temperature above at least 200 C., the ratio of water to the crude product being on a weight basis 2:3, subsequently heating the resulting mixture to a temperature between 250 and 280 C. and finally separating the ethyleneurea from the resulting product.

5. In a-process for the preparation of ethyleneu-rea from ethylene glycol and urea, the step which comprises continuously passing water and the reaction product, obtained by heating ethylene glycol and urea, the urea being ,present in excess, to a temperature between about 150-and about 250 0., through a reaction zone maintained at a temperature sufficient to heat the mixture to between 200 and 300 0., wherein the mixture is at temperature for at least 25 minutes.

6. In a process for the preparation of ethylene urea from ethylene glycol and urea, the steps which comprise preparing a crude melt by the interaction of a .mixture of urea and ethylene glycol having a molecular weight ratio .of approximately 3.5:1 respectively, by heating to a temperature of approximately 250 16., discharging the resulting reaction product into water to give 1 /2 lbs. of waterper 1b. of therea'ction product, further diluting the mixture to give approximately 6.3 pounds-of crude mixture to 9.5 pounds .of water, and subsequently continuouslypassing the mixture through a heated reaction chamber wherein it is maintained at a temperature of about 250 C. for approximately 35 minutes, and finallyrecovering the 'ethyleneureai from the resulting product :by distillation.

'7. A continuous process .forithe preparation of ethyleneureawhich comprises continuously passing a mixture of ethylene glycol and urea, the ureabeing present in ex'cess into areaction zone maintained at a temperature between 200 and 300 C. whereby an intermediate product "is obtained, continuously converting said intermediate product in the presence of water to ethyleneu-rea by heating to a temperature 'between'200 and 300 C. and continuously separating the ethyleneurea from the react-ion mixture :by rectification.

8. In a process for the preparation of ethyleneurea from ethylene glycol and urea, the step which comprises treating with Water and at a temperature between 2:00 and 300 C. the reaction product obtained by heating ethylene glycol and urea, the urea being present in EXCESS, to 'a temperature between about 150 and about 250 'C/ 9. In a process for the preparation of'ethyleneurea 'from ethylene glycol and urea, the :step which comprises treating with water and at a temperature between 25.0 and 280 C. the reaction product obtained by heating ethylene glycol and urea, the urea being present "in excess, to a temperature between about 150 and about 250 'C.

10. In a process for the preparation of :ethyleneurea "from ethylene glycol and urea, the step which comprises subjecting to steam distillation the reaction product obtained by heating ethylene glycol and urea, the urea being present in excess, .to .a temperature between about 1 50 and about 250" C.

DONALD J. LODER.

REFERENCES CITED The following references are of record in the 5 file of this'patent:

UNITED STATES PATENTS 

